Conventionally, there is a device shown in Patent Literature 1 as a power source outlet device having a function of preventing tracking. In a technique of Patent Literature 1, an electrically conductive plate is disposed in plug insertion holes on a front face of a power source outlet device, one end thereof being protruded from a surface while another end thereof being connected to a ground terminal, so that a leakage current occurring between plug blades is led to flow to the ground terminal via the electrically conductive plate before tracking occurs and a cable run is disconnected by letting a leakage breaker detect the leaked current.
However, in the above-described conventional power source outlet device, since an electrically conductive plate serving as a sensor is exposed to a surface of a cover of the power source outlet device, malfunction may occur when an electrically conductive material comes in contact with the electrically conductive plate. Further, a user's hand or the like may touch the sensor, and such exposure is not desirable.
In view of these circumstances, the present applicant has proposed a power source outlet device where a through-hole is provided without exposing a sensor to a surface of a cover of the power source outlet device so that a spark discharge (scintillation) between plug blades which causes a tracking phenomenon can be detected inside the cover in Patent Literature 2. In the power source outlet device, such a method is adopted that a sensor is disposed on a back face of the cover as a sensor mounting structure, and the sensor is fixed being covered its back portion with insulator such as resin.
[Patent Literature] JP-A-2001-35599
[Patent Literature] JP-A-2004-327247